I've built maybe 6 or 7 sets of headers for projects over the years. It seems like when you hit that phase of a project and you have-to/want-to fab them, it is a major time-suck and your project drags for a while.
Rob McCabe had a custom header shop in Phoenix and I stopped and visited him for one of my projects a long time ago. I couldn't afford his headers but he took a half hour and showed me some of his techniques and encouraged me to try it myself. Nice guy. He has a shop in Chino Valley which is near Prescott AZ.
http://www.mccaberacing.com/
If time is at a premium and you have to have long tubes, he might be a solution.